audio: new audio devices enums

Changed audio device API version to 2.0 because of
new enums for audio input and output devices.

Removed implementations of get_supported_devices() in
stub and usb audio modules.

Change-Id: I09345d38929d931e5015e36d18259f5a5f950298
diff --git a/include/hardware/audio.h b/include/hardware/audio.h
index 4fd73a2..3a0962e 100644
--- a/include/hardware/audio.h
+++ b/include/hardware/audio.h
@@ -53,7 +53,8 @@
  */
 #define AUDIO_DEVICE_API_VERSION_0_0 HARDWARE_DEVICE_API_VERSION(0, 0)
 #define AUDIO_DEVICE_API_VERSION_1_0 HARDWARE_DEVICE_API_VERSION(1, 0)
-#define AUDIO_DEVICE_API_VERSION_CURRENT AUDIO_DEVICE_API_VERSION_1_0
+#define AUDIO_DEVICE_API_VERSION_2_0 HARDWARE_DEVICE_API_VERSION(2, 0)
+#define AUDIO_DEVICE_API_VERSION_CURRENT AUDIO_DEVICE_API_VERSION_2_0
 
 /**
  * List of known audio HAL modules. This is the base name of the audio HAL
@@ -329,6 +330,12 @@
      * each audio_hw_device implementation.
      *
      * Return value is a bitmask of 1 or more values of audio_devices_t
+     *
+     * NOTE: audio HAL implementations starting with
+     * AUDIO_DEVICE_API_VERSION_2_0 do not implement this function.
+     * All supported devices should be listed in audio_policy.conf
+     * file and the audio policy manager must choose the appropriate
+     * audio module based on information in this file.
      */
     uint32_t (*get_supported_devices)(const struct audio_hw_device *dev);